I mean really ?!? Plastic cam AND plastic lobes ???? But how much weight and money is Briggs saving here ?!?! Planned absolesence.....what a disgrace. Disposable mower engines now. Just threw out a trash picked 1972 Briggs push mower. Ran it for 7 years. Smokin like crazy, blow by was insane, piston rod rap was so loud, it was ridiculous. My neighbors hated it. Frig em...LOL . Got to the point where I was runnin pure STP oil treatment in the crankcase. I said, ok, this is enough now. Costing me more in STP than gasoline. Wheeled it out to the trash. I BET there was not a single piece of plastic in that engine to run on pure STP blue bottle. It would have never taken the abuse. Now, that was an engine !!!!!!! Now I have some 1/2 plastic P.O.S. from Home Depot, with a Briggs on it no less.
Briggs & Straton OHV Plastic Engine No Compression
- Thread starter Montecore
- Start date
I found the reason for compression loss, in the first picture the spark plug is gone. 
Briggs has been using plastic cams and gears since the 1970s, most of the flatheads people rave about being so great have plastic components, I'm pretty sure every just about every consumer Briggs since they had soiid state ignition has used a nylon cam, The entire lifespan of the quantum they used plastic components, I took apart a quantum that was on a mower I trashpicked a few years ago, the deck was much newer but I believe the engine was from about 1989 (the starter/shroud had been replaced) but it had the old style gas tank which fully covered the starter with only the small circular piece that popped in for branding and it was only rated for 4HP and the molding on the gas tank looks like it was date coded for 1989 because I know they didn't make that style still in 1999. But the cam was still alright in that engine even tho the rod was now wireless.
Exhaust valve definitely looks wonky.